1. Field of the Invention
The present invention relates in general to a virtual machine system for accessing external subprogram functions and, more particularly, to a bootable virtual machine system allowing independent access to and update of ROM memory and RAM memory.
2. Description of the Prior Art
Some object-oriented computer languages, such as JAVA, utilize classes which cannot be executed directly from read-only ("ROM") memory. To create a bootable operating system using such computer languages, known techniques have been developed to store object-oriented class files in ROM. These class files are stored in a module in a manner which allows the class files to be executed directly from ROM. Such modules are often referred to as "ROMmed" modules. Main memory RAM is typically coupled to the ROMmed module to allow execution of functions. While ROMmed modules do allow the creation of bootable operating systems using classes, systems utilizing such ROMmed modules have several drawbacks.
One drawback with such prior art systems is the difficulty in accessing and/or updating the RAM and ROM memory independently of one another. Prior art systems typically include a RAM portion and a ROM portion. The ROM portion typically includes proprietary class files while the RAM memory is utilized to execute various functions in association with a particular program. Because of the distinct aspects of the two types of memory, it often becomes desirable to update and/or access one type of memory without disturbing the other. In prior art systems, the ROM memory and RAM memory are so integrally connected that it is not possible to readily separate the two types of memory for independent access or update.
While it would be desirable to separate the two types of memory, an additional problem associated with prior art systems is that such systems do not provide means for separating out the aspects of the system required for accessing external functions. Accordingly, even if prior art systems could be divided into integral RAM and ROM components, it would not be possible to update one without having detailed knowledge of the workings of the other. Since many such systems contain proprietary information in the ROM module, it would be desirable to provide means for updating the ROM module without requiring access to such proprietary information.
The difficulties encountered in the prior art noted herein above are substantially eliminated by the present invention.